SmedSpeed XS650

 


CAMSHAFTS

Smedspeed now stocks performance cams for your stock 360 degree phased engine. Using the very same high performance Landis 3L cam grinding machine that the rephased cams are manufactured on, also offered are reground stock cams  These cams utilise your existing cam core and have a performance profile ground onto it. The use of your stock core keeps the price down.  
The well renowned flat track Shell #1 and the early Yamaha XS1/XS2 profiles are available.

The 750 big bore engines run extremely well on either of these "softer" cam profiles, producing strong torque from 2000rpm upwards. The downside (and there is always one) is the outright top end is only in the region of 55 hp rear wheel. 

The cams are on an exchange basis, the cam given for exchange must be a usable core.

Please call for details, they are usually in stock for immediate dispatch. 


CAM PROFILES

Smedspeed camshafts in 277 rephased and 360 degree (stock) are available  with any of the profiles listed below. The cams are produced in the UK from an EN40B billet of steel. All come with an adjustable sprocket, which facilitates truly accurate cam timing, which can assist in changing the rpm at which peak torque occurs. This lowers or raises the power in the rev band.

Also available are reverse pattern cams, for those that might wish to reverse the cylinder for racing, or just to be cool.

Yamaha XS1/ XS2 cam
Original equipment cam for 1970-1973. Nice cam for 650/750 strong low end and mid range. Used in a lot of 750 conversions, particularly where the client does not wish to rev the engine hard to get strong performance.  A few of the after market cams are too much for a 650cc engine,  and are almost too much for a 750 engine. This cam is NOT one of these.  Easy install.

Megacycle 250-20
Mild street cam. No pronounced power-band, relatively small improvements over whole rpm range. Not one of my favourites at all. 0.400’’ lift; there are much better cams than this.

Smedspeed 2.5. A 250-20 with more overlap which requires a good exhaust system to work well. This was a design done in-house using the latest cam design software at our cam grinders facility. 

Shell #1
The classic flat track cam. Really good low end and midrange, good top end but not overly powerful at very high rpm. Easy install with 0.410’’ lift. Needs more compression on a 650 engine, or 750cc. Needs good valve springs.  

Yamaha race accessory cam
A direct copy of the Yamaha Race accessory cam available in 1972.  Lower lift means easy installation, not really much different from a Shell # 1. The cam Yamaha suggested you run with a 750 race kit.  

Megacycle 250-00
Street cam, improved mid range power needs higher compression than stock OR 750cc. Late inlet closing. 0.420" lift. Needs good springs.

Megacycle 250-30
A really good hot/wild street cam. 0.440’’ lift, needs 10:1 compression to work well, but gives very strong midrange and top end, and can be adjusted to give stronger bottom end too at the expense of some top end loss. Really good hot street cam for 750 cc and bigger engines. Needs shorter valve guides/valves recessing, and good valve springs. Long duration which makes the part throttle bottom end a bit fluffy.

Smedspeed 3.5 cam . The Megacycle 250-30 was modified to ensure the power was all within the max rpm rev band.  This cam has been used by ALL the racers we know, and its very good. Really only for a 750 and bigger, and then it must have more compression, needs 9:1 minimum, .440'' lift
A really good hot street cam

Megacycle 250-40 
Race cam, drag racing, hill climbing, 0.480’’ lift needs 11:1 compression to make it work properly. A real race cam, don’t run this on the road, noisy valve gear, fast guide wear. Needs good springs, all clearancing work undertaken, not easy to install at all.

Smedspeed 666 cam. This was designed by Howard and Ken Newman over a cup of coffee around three years ago. It was specifically for the hi performance 880 that Steve Mann has built with raised inlet port and a whole host of tricks. This is a high torque cam, but requires a big engine or a small one revving high, will be fitted to the short stroke engine we build. 520'' inlet and 0.480'' exhaust, needs good springs, shortened guides, the whole deal.

A word about cam choice : DO NOT overcam your engine. If in any doubt speak to us, we know what will work, engines run on combinations of parts and no idea what shiny item you have bolted in !!


rocker arms and cam timing

When the Yamaha XS650 left the factory, the rocker arms were manufactured with a precisely ground radius on the area that contacts the cam and this was then hard chrome plated. Over many years the hard chrome wears, mostly due to extended oil changes, oil with no ZDDP in it, bad filtration and just general wear and tear (abuse). This wear has an adverse effect on the cam timing. Pictured below is a rocker arm I took out of a running engine. It did sound like a bag of bolts, but it was running nevertheless. This is the worst example I have seen, but many rocker arms which look good are not within specification, and the accumulated wear will only get worse over time.

Worn rocker arm

As part of my engine rebuilds, I dial in the cam timing using a degree wheel and a dial gauge mounted on the valve spring top collar. This way the cam timing can be set very accurately, and also any manufacturing discrepancy in the cam or the rocker arms can be traced. The performance and rephased cams I supply are ground on a Landis 3L cam grinding machine, many of the USA based cam manufacturers use this same equipment, it is state of the art, so I am entirely confident the cams are not the variable.

Landis 3L
 
I often find that my cam timing figures are not what I expect, sometimes way off what they should be, and this is invariably attributed to worn rocker arms. The chrome plating wears away and the radius "flattens" or small gouges are evident, all of which affect the valve opening duration, the cam lift strangely is essentially unaffected. To remedy the situation I have found a firm who can recondition the OEM rocker arms by replacing the radiused part of the rocker arm with a brazen on radiused stellite pad. This technology has been used to reclaim many thousands of Ducati rocker arms which also suffer the same fate as the XS650 items. The performance cams I provide are made from EN40B steel and then case hardened. The Stellite/EN40B is an ideal combination for a long lasting hard wearing valve gear.

Reconditioned rocker arm

So why bother at all I hear you say? There are many reasons for doing something properly, not least just to get it right. If you are fitting a new cam, whether it is for more performance or as part of a rephased engine build, it seems pointless not to do it the best it can be.

The engine builds are not in the main dedicated racing engines, just strongly built high torque engines. This increased torque allows the bike to run higher gearing to cope with increased traffic speeds. Worn rocker arms translate the duration of what was a very mild cam in the first place into something more suitable for a lawn mower. A good mild street cam coupled with refaced rocker arms will really bring your engine to life.



Contact me for more details


DISCLAIMER
These are experimental parts intended for racing and as such no warranty is given or implied. If you decide to buy it is on the understanding that you assume complete responsibility for any possible injury, loss or damage that may occur as a result of using these parts and that you accept these conditions of sale prior to purchase.